Biomedical subjects

D A Ronken

Publications and source records attributed to D A Ronken.

11 recordsLinked to original sources

PubMed1993

Effects of spike discharge history on discharge probability and latency in frog basilar papilla units.

Gaumond et al. [(1982) J. Neurophysiol. 48, 856-873] showed in the cat that a multiplicative-intensity model can generally account quite well for reduction of the probability of an auditory-nerve spike by another spike preceding it by 4 to 25 ms, and that for smaller separations there is also an increased latency of the following spike. Bosch [(1990) D. Sc. Dissertation, Washington University, St. Louis, MO] made important improvements in experimental design and estimation techniques for studying these effects, and confirmed their presence in the gerbil. However, direct application of these methods to the frog does not yield reliable estimates. A clearer separation of discharge probability and latency effects in frog basilar papilla units is provided by the paired-click paradigm used in this study, which is applicable to low-spontaneous-rate units that generally respond to click stimuli with zero or one spike within a short interval following the click. The results confirm the existence in the frog of both spike-probability and spike-latency effects that are qualitatively similar to those found in mammals, although the absolute refractory time is much longer in frog, and the relative refractory time usually shorter. The paired-click paradigm also reveals a stimulus-history effect at stimulus levels which are near threshold: when there is no response to the first click, responses to the second click occur with increased probability and reduced latency.

Acoustic Stimulation↗

PubMed1991

Spike discharge properties that are related to the characteristic frequency of single units in the frog auditory nerve.

Single units from the auditory nerve of frogs and toads have their receptor cells located in two separate sensory organs that provide disjoint frequency ranges. The amphibian papilla (ap) provides units with characteristic frequency (CF) in the low- and mid-frequency regions and the basilar papilla (bp) provides units with high CF. There are gross differences in both the mechanical design and innervation patterns of the two organs, so that one might expect discharge properties for units with different CF to differ in many respects. However, there have been few reports of response attributes that correlate strongly with CF for units in the mid- and high-CF regions. Measurements of automated tuning curves from 250 units in Rana pipiens show that W10 dB, the bandwidth of the tuning curve measured 10 dB above CF threshold, is consistently larger for high-CF units than for low- and mid-frequency units. When units are classified into three groups by an objective statistical method using only CF and W10 dB measurements, the groups appear to correspond reasonably well with the low-, mid-, and high-frequency categories identified in many other studies.

Acoustics↗

PubMed1990

Basic properties of auditory-nerve responses from a "simple' ear: the basilar papilla of the frog.

Spike discharges initiated by mammalian inner hair cells are produced by a complicated system involving both mechanical and neural components that normally operate in a bi-directional configuration involving multiple feedback loops. In contrast, the frog basilar papilla has the equivalent of inner hair cells, but lacks outer hair cells; it has no efferent system, and no basilar membrane. This suggests that the frog basilar papilla lacks some of the mechanical and neural feedback paths characteristic of the mammalian system. Detailed measurements of tuning curves, spontaneous activity and responses to tones an clicks reveal large parametric differences between frog and mammals in spontaneous rate, absolute refractory time, long-term adaptation and phase locking. Responses to tone bursts are qualitatively similar, but parametrically quite different. More focused examinations of these effects will be able to exploit the differences in adaptation to long- versus short-duration stimuli could be caused by depletion of afferent neurotransmitter or by activation of feedback loops involving the efferent system. In the basilar papilla, any differences in adaptation must result from changes in the afferent pathway alone.

Acoustic Stimulation↗

PubMed1986

Anomalous phase relations in threshold-level responses from gerbil auditory nerve fibers.

Phase-locked responses at near-threshold levels obtained from single units in the auditory nerve of gerbils show that the relation between phase lag and linear frequency often contains an unexpected microstructure. In frequency regions below 1 kHz that are also an octave or more below CF, phase curves often have multiple straight-line segments, rapid slope changes, or other major inflections. These detailed features of the phase curves are not accounted for by any identified artifact. For example, the anomalous features cannot be removed simply by lowering the stimulus level; they remain down to levels where phase locking first occurs. Phase curves for single units with the same CF recorded from different animals can have similar microstructures, suggesting that the form of the phase curves may reflect some joint effect of stimulus frequency and CF or longitudinal position.

Animals↗

PubMed1981

Identification of local and propagating distortion products from cochlear microphonic responses.

Careful measurements show that sound pressures of 40 dB re 20 mu N/m2 are sufficient to reveal two varieties of well-behaved, nonlinear distortion products in the cochlear microphonic (CM). The first variety appears in the primary-tone area and is designated as a local CM distortion product. The second type exists apical to the primary-tone area and is identical to the mechanically propagated distortion seen in the phase-locked responses of primary auditory nerve fibers. The existence of the propagating distortion product forces the conclusion that there must be a mechanical contribution to the local "CM" distortion product as well. The intrusion of nonlinear mechanical responses at such low levels (less than 40 dB SPL) indicates that the effective mechanical input to the hair cells may be nonlinear over most of the audible range. An important but unanswered question is the range over which the transducer characteristic of CM could be effectively linear, for that would determine whether CM could be used to probe mechanical nonlinear effects in the primary tone area.

Acoustic Stimulation↗

PubMed1973